Montreal dumping 8 billion litres of sewage into St. Lawrence River this Wednesday

DH Vancouver StaffNov 10, 2015 8:41 pm

At the stroke of midnight Eastern Time on Wednesday, crews with Montreal’s municipal government will divert eight billion litres – equivalent to the volume of 3,200 Olympic swimming pools – of sewage directly into the St. Lawrence River. But why?

According to Ville de Montreal, it’s necessary in order to complete a week-long repair and maintenance project in the Southeast Interceptor, a 30-km-long trunk sewer.

The repairs involve replacing a snow chute, which are used in the winter months when snow cleared from roads and surfaces is dumped into chutes as part of the snow-clearing process. Other elements to the repairs include replacing valves and removing the sewer’s wooden structures as falling wood has been falling into the water and clogging the water treatment facility.

The work cannot be completed unless the sewer is emptied out and dried before the season’s snowfall, and there is no other feasible alternative. Critics have argued that a secondary interceptor should be constructed, but that could take years to build and would see rare use. In contrast, the repairs being undertaken this month will cost just $2.2 million.

Trucking the waste water away is also unfeasible as it would require tens of thousands of truck trips per day, whereas the approved plan will allow 12,000 litres per second of sewage water to flow directly into the river out of 24 outfall pipes. The entire process will take seven days.

The plan was approved by the federal Liberal government on Monday, with stipulations that the municipal government must include emergency measures. The sewage dump was originally scheduled to begin on October 18, the day before the federal election.

But the dump was postponed by the Conservative government just days before the election as former federal Environment Minister Leona Aglukkaq ordering an independent scientific review into the plan and whether there are other feasible solutions.

The wastewater dump in late-fall is strategic as the fish spawning season over and the lower temperatures reduce the spread of bacteria. It is anticipated the sewage will dilute in the St. Lawrence’s fast-moving waters – about 7 million litres per second.

By 2018, Montreal aims to have 99.99 per cent of all waste water treated within metropolis region limits. As well, all waste water discharged into the river will be disinfected and ozonized.

And in five years, five new sewage holding tanks will be constructed in order to reduce the likelihood of sewage overflows into the river.